Hypersecretion of anterior pituitary hormones

Question 1

What is hyperpituitarism?

Answer 1

Symptoms associated with excess production of adenohypophysial hormones

Question 2

What is hyperpituitarism usually caused by?

Answer 2

Isolated pituitary tumours (can also be ectopic - ie: non endocrine tissue)

Question 3

What are some symptoms associated with hyperpituitarism?

Answer 3

Visual field and other cranial nerve defects, as well as endocrine signs and symptoms

Question 4

How does hyperpituitarism lead to visual field defects?

Answer 4

Suprasellar pituitary tumours pressing on the optic nerves in the optic chiasm causing bitemporal hemianopia

Question 5

What is bitemporal hemianopia?

Answer 5

Loss of peripheral vision in both eyes

Question 6

What can excess ACTH lead to?

Answer 6

Cushing’s disease

Question 7

What can excess TSH lead to?

Answer 7

Thyrotoxicosis/hyperthyroidism

Question 8

What can excess FSH and LH lead to?

Answer 8

Precocious puberty in children

Question 9

What can excess prolactin lead to?

Answer 9

Hyperprolactinaemia

Question 10

What can excess GH lead to?

Answer 10

Gigantism/Acromegaly

Question 11

What are the causes of hyperprolactinaemia?

Answer 11

Physiological
>pregnancy
>breastfeeding

Pathological
>prolactinoma

Question 12

What is the most common functioning pituitary tumour?

Answer 12

Prolactinomas

Question 13

Why do prolactinomas cause infertility?

Answer 13

Because high levels of prolactin suppress GnRH pulsatility.

Question 14

What are some symptoms of hyperprolactinaemia due to pituitary adenomas in women?

Answer 14

> Galactorrhoea
Secondary amenorrhoea or oligomenorrhoea
Loss of libido
Infertility

Question 15

What are some symptoms of hyperprolactinaemia due to pituitary adenomas in men?

Answer 15

> Galactorrhoea (uncommon bcs appropriate steroid background usually inadequate)
Erectile dysfunction
Loss of libido
Infertillity

Question 16

How is prolactin secretion regulated?

Answer 16

Dopamine from hypothalamic dopaminergic neurones binds to D2 receptors on the lactotrophs and switches OFF prolactin secretion.

Question 17

What is the first line treatment for hyperprolactinaemia?

Answer 17

Dopamine receptor (D2) agonists orally administered (NOT SURGERY)

Question 18

Name some examples of dopamine receptor agonists

Answer 18

Bromocriptine

Cabergoline

Question 19

What do dopamine receptor agonists do in patients with hyperprolactinaemia

Answer 19

Decrease prolactin secretion

Reduce tumour size

Question 20

What are some side effects of the dopamine receptor agonists?

Answer 20

>nausea and vomiting
>postural hypotension
>dyskinesias 
>depression
>impulse control disorder (eg:pathological gambling, hypersexuality)

Question 21

What does excess growth hormone result in in childhood and in adulthood?

Answer 21

Gigantism in childhood

Acromegaly in adulthood

Question 22

What is excess GH usually caused by?

Answer 22

Benign growth hormone secreting pituitary adenoma

Question 23

What are some reasons why people with acromegaly die?

Answer 23

Cardiovascular disease 60%
•Respiratory complications 25%
•Cancer 15%

Question 24

Why is it so difficult to diagnose acromegaly?

Answer 24

It’s insidious in onset, so signs and symptoms progress gradually.

Question 25

What grows in acromegaly?

Answer 25

• periosteal bone
• cartilage
• fibrous tissue
• connective tissue
• internal organs (cardiomegaly, splenomegaly, hepatomegaly, etc.)

Question 26

What are some clinical features of acromegaly?

Answer 26

• excessive sweating (hyperhidrosis)
• headache
• enlargement of supraorbital ridges, nose, hands and feet, thickening of lips and general coarseness of features
• enlarged tongue (macroglossia)
• mandible grows causing protrusion of lower jaw (prognathism)
• carpal tunnel syndrome (median nerve compression)
• barrel chest, kyphosis

Question 27

What are the metabolic effects of acromegaly?

Answer 27

Excess GH -> increased endogenous glucose production, decreased muscle glucose uptake -> increased insulin production = increased insulin resistance -> impaired glucose tolerance -> diabetes mellitus

Question 28

What are the complications of acromegaly

Answer 28

• Obstructive sleep apnoea
–Bone and soft-tissue changes surrounding the upper airway lead to narrowing and subsequent collapse during sleep
•Hypertension
–Direct effects of GH &/or IGF-1 on vascular tree
–GH mediated renal sodium reabsorption
•Cardiomyopathy
–Hypertension, DM, direct toxic effects of excess GH on myocardium
•Increased risk of cancer
–Colonic polyps, regular screening with colonoscopy

Question 29

Why is prolactin often high in acromegaly?

Answer 29

May reflect tumour secreting GH and prolactin

Question 30

How is acromegaly diagnosed?

Answer 30

• GH pulsatile – so random measurement unhelpful
• Elevated serum IGF-1
• Failed suppression (‘paradoxical rise’) of GH following oral glucose load – oral glucose tolerance test. Normally people have a low GH response to oral glucose load but in acromegaly, GH increases.

Question 31

What is the first line treatment for acromegaly?

Answer 31

Trans-sphenoidal surgery

Question 32

What are some medical treatments for acromegaly

Answer 32

Somatostatin analogues
> EG: octreotide
Dopamine agonists (GH secreting pituitary tumours frequently express D2 receptors)
>EG: cabergoline

Question 33

What are some side effects of somatostatin analogues?

Answer 33

GI effects - nausea, diarrhoea, gallstones

Question 34

How does somatostatin analogue help with acromegaly?

Answer 34

Reduces GH secretion and tumour size. Pretreatment before surgery can make resection easier. Used post-operatively if not cured or whilst waiting for radiotherapy to take effect - bcs radiotherapy slow